The present invention relates to a rolling apparatus and more particularly to a rolling apparatus comprising a lubricant composition.
In general, a rolling apparatus such as rolling bearing and direct-acting apparatus comprises a lubricating oil such as mineral oil and poly-xcex1-olefin oil or a lubricant such as grease enclosed in a circulating apparatus or thereinside to effect lubrication and thereby protect itself and members in contact therewith against abrasion or other damage.
Such a rolling apparatus can be used without any problems under normal working conditions. However, when such a rolling apparatus is used under high temperature conditions, reduced pressure or high speed conditions, the lubricant or grease is scattered out of the rolling apparatus or evaporated to produce a gas, causing contamination of the external atmosphere of the rolling apparatus. Therefore, a fluorine-based grease has heretofore been often used as a lubricant for rolling apparatus for uses requiring clean atmosphere such as clean room, semiconductor producing machine, liquid crystal panel producing machine and hard disc producing machine and apparatus which are used under high temperature conditions or under reduced pressure.
The fluorine-based grease is a mixture of a base oil composed of liquid fluorinated polymer oil and a thickening agent composed of solid fluorinated polymer. Because of its extremely low volatility, the fluorine-based grease is scattered out of the rolling apparatus in a relatively small amount (blown-up amount). Accordingly, the fluorine-based grease can cause relatively little contamination of the external atmosphere of the rolling apparatus.
However, this fluorine-based grease is inferior to the grease comprising a lubricating oil such as mineral oil and poly-xcex1-olefin in fluidity and lubricity. Thus, when a rolling apparatus comprising such a fluorine-based grease is operated, it is liable to cause abrasion on the rolling elements and members in contact therewith. This abrasion is a serious problem particularly with a direct-acting apparatus for use in positioning apparatus in semiconductor or liquid crystal panel producing apparatuses because it deteriorates the positioning accuracy.
Further, dust produced by this abrasion enters in the lubricant, possibly causing torque fluctuations or torque rise or seizing in a relatively short period of time. This torque rise causes deterioration of positioning accuracy or heat generation or overload on a motor.
In recent years, the operation speed of semiconductor or liquid crystal panel producing machines has been raised more and more. Accordingly, it has been required for rolling apparatuses to operate at high speed. Therefore, these rolling apparatuses are more liable to torque rise due to dust blowing or abrasion caused by the lubricant scattering. It has thus been desired to minimize dust blowing and improve torque life.
As an approach for solving these problems there has been known a method involving the use of a lubricant comprising molybdenum disulfide, tungsten disulfide or graphite incorporated therein. The use of such a lubricant makes it possible to improve the load resistance, seizing resistance or boundary lubricity of the rolling apparatus.
However, since molybdenum disulfide or graphite is black, it can color an object to be treated such as a liquid crystal panel and a semiconductor substrate when the lubricant is scattered. Further, molybdenum disulfide and tungsten disulfide contains metallic elements such as molybdenum and tungsten. Therefore, when the lubricant is scattered, the metallic elements incorporated in the lubricant are attached to the object to be treated such as a semiconductor substrate, possibly causing troubles such as defects and short-circuiting.
An object of the present invention is to provide a rolling apparatus which exhibits reduced dust blowing and prolonged torque life, more specifically, a rolling apparatus which is suitable for use in an apparatus requiring a clean atmosphere such as clean room, semiconductor producing apparatus, liquid crystal panel producing apparatus and hard disc producing apparatus and exhibits minimized dust blowing and prolonged torque life at high temperatures, in vacuo or under other severe conditions.
Another object of the present invention is to provide a rolling apparatus which exhibits minimized dust blowing and prolonged torque life and causes no troubles on an object to be treated such as a liquid crystal panel and a semiconductor substrate even if the lubricant is scattered.
The present invention provides the following rolling apparatuses.
(1) A rolling apparatus comprising:
a movable member which can undergo rotary or linear motion,
a support member which carries the movable member,
rolling elements which are interposed between the movable member and the support member and which roll with the movement of the movable member, and
a lubricant composition which is disposed between the movable member on which the rolling elements roll and the support member,
wherein the lubricant composition is a mixture of (1) a thickening agent which is at least one selected from the group consisting of a solid fluoropolymer, a lamellar mineral powder, an ultrafinely particulate organic material, an organic solid lubricant and an ultrafinely particulate inorganic material, and (2) a base oil comprising a liquid fluorinated polymer oil.
(2) The rolling apparatus of item (1), wherein the lubricant composition further contains an oily compound having a perfluoropolyether skeleton as a main chain and a polar group at either or both ends of the main chain and having a molecular weight of not more than 10,000 in an amount of from 0.5 to 10% by weight.
(3) The rolling apparatus of item (1) or (2), wherein the lubricant composition contains the thickening agent in an amount of 0.1 to 45% by weight and the base oil in an amount of 55 to 95% by weight.
(4) The rolling apparatus of item (1) or (2), wherein the lubricant composition contains the lamellar mineral powder having an average particle diameter of 0.05 to 20 xcexcm in an amount of 1 to 45% by weight.
(5) The rolling apparatus of item (1) or (2), wherein the lubricant composition contains the ultrafinely particulate inorganic material having an average particle diameter of 0.1 xcexcm or less in an amount of 0.1 to 20% by weight.
(6) The rolling apparatus of item (1) or (2), wherein the lamellar mineral powder is at least one selected from the group consisting of a mica-based mineral, a vermiculite-based mineral and a montmorillonite-based mineral.
(7) The rolling apparatus of item (1) or (2), wherein the ultrafinely particulate inorganic material is at least one selected from the group consisting of SiO2, MgO, TrO2, Al2O3, diamond, and fullerence (C60).
(8) The rolling apparatus of item (2), wherein the lubricant composition comprises the oily compound consisting of a perfluoropolyether carboxylic acid having a molecular weight of not more than 10,000 in an amount of from 0.5 to 10% by weight.
(9) The rolling apparatus of item (1) or (2), wherein the lubricant composition contains at least one of the ultrafinely particulate organic material and the organic solid lubricant in an amount of 1 to 45% by weight.
(10) The rolling apparatus of item (1) or (2), wherein the ultrafinely particulate organic material has an average particle diameter of 20 nm to 1 xcexcm.
(11) The rolling apparatus of item (1) or (2), wherein the ultrafinely particulate organic material is an ultrafinely particulate polymer and is at least one selected from the group consisting of a polymer or copolymer of acrylic acid ester, a polymer or copolymer of methacrylic acid ester, a styrene polymer, a styrene-acryl copolymer, and a styrene-methacrylic acid ester copolymer.
(12) The rolling apparatus of item (9), wherein the ultrafinely particulate organic material is spherical and hydrophobic.
(13) The rolling apparatus of item (9), wherein the organic solid lubricant has a white lamellar crystal structure and is at least one selected from the group consisting of an amino acid compound, melamine cyanurate and a carbon fluoride.
(14) The rolling apparatus of item (9), wherein the organic solid lubricant has an average particle diameter of 0.05 to 20 xcexcm.